The invention relates to a lighting system according to the preamble to patent claim 1.
Such a lighting system is disclosed, for example, in German Laid-Open Specification DE 196 10 385 A1. This document describes a high-pressure discharge lamp for motor vehicle headlamps, which has a lamp vessel of glass, two electrodes and a lamp base provided with electrical connections. A control unit for the high-pressure discharge lamp is integrated in the lamp base. The control unit usually has a considerably longer service life than the high-pressure discharge lamp. However, since the control unit is inseparably integrated in the lamp base, it cannot continue to be used if the lamp is faulty, but has to be replaced together with the faulty lamp.
The object of the invention is to avoid the disadvantage of the lighting system according to the prior art.
The invention achieves this object as a result of the distinguishing features of patent claim 1. Particularly advantageous refinements of the invention are described in the subclaims.
The lighting system according to the invention has a high-pressure discharge lamp and a control unit for the high-pressure discharge lamp, the high-pressure discharge lamp having at least one lamp vessel, electrodes and an illuminant for producing a gas discharge, as well as a base provided with electrical connections. The base additionally has fastening means for the at least one lamp vessel. The control unit has an ignition device which is accommodated in the base and has a high-voltage part. According to the invention, the base has at least two housing parts, which are connected to one another by a releasable closure, the first housing part having the fastening means for the at least one lamp vessel, and the high-voltage part being accommodated in the first housing part, whereas the second housing part is provided with the electrical connections for the high-pressure discharge lamp.
The aforementioned measures according to the invention allow the second housing part, with the components arranged in it, to continue to be used if the high-pressure discharge lamp is faulty, in that the closure between the first and the second housing part is released. The first housing part is replaced together with the faulty high-pressure discharge lamp fastened to it. For technical safety reasons, the invention provides for the first housing part to accommodate the high-voltage part, advantageously comprising a transformer, of the ignition device, said high-voltage part having to be replaced together with the faulty high-pressure discharge lamp. The high-voltage part of the ignition device is advantageously embedded in a potting compound which improves its electrical insulation. In addition, the high-voltage connection, connected to a lamp electrode, of the high-voltage part is advantageously also embedded in the potting compound for the same purpose.
The further components of the ignition device, such as the ignition capacitor and the spark gap, are advantageously arranged in the second housing part. As a result, these components of the ignition device need not be replaced if the high-pressure discharge lamp is faulty. The further components of the ignition device are advantageously arranged on a support plate, which can easily be inserted into the second housing part. The at least two housing parts are advantageously connected to one another releasably by a snap-fit or screw-fit closure or by a plug connection. In addition, the first housing part advantageously has first electrical contacts and the second housing part has second electrical contacts, between which an electrically conductive connection is made when the first and the second housing part are connected to one another. The first and second electrical contacts of the housing parts advantageously form a plug connection which is produced automatically when the at least two housing parts of the base are fitted. This ensures that the lamp base is easy to assemble.
At least one housing part of the base is advantageously fitted with a cooling device which dissipates heat generated by the control unit. In addition, the first and/or the second housing part are shielded against electromagnetic radiation, which improves the electromagnetic compatibility of the lighting system according to the invention.
The control unit in the lighting system according to the invention has, in addition to the ignition device, a voltage converter which is advantageously designed as an inverter, for example as a half-bridge or full-bridge inverter, as a push-pull inverter or as a single-ended converter. This voltage converter is advantageously arranged on the same support plate as the aforementioned further components of the ignition device. This means that the whole control unit for the high-pressure discharge lamp can be accommodated in the base of the lamp. The arrangement is particularly compact and advantageous if the aforementioned voltage converter is designed as an integrated circuit.
The invention can be applied particularly advantageously to a lighting system with a high-pressure discharge lamp with a base at one end and with one electrode near to and one remote from the base. Such a lighting system is used in a motor vehicle headlamp, for example. The at least one high-voltage connection of the high-voltage part of the ignition device is in this case advantageously connected to that electrode of the high-pressure discharge lamp that is near to the base. This ensures that those parts carrying high voltage are enclosed inside the first housing part or the lamp vessel such that they are protected from accidental contact. In addition, this means that the electrical connections of the base of the high-pressure discharge lamp have only the comparatively low vehicle supply voltage of the motor vehicle applied to them. That electrode of the high-pressure discharge lamp that is remote from the base, and the connections of the primary of the transformer in the ignition device, are advantageously electrically conductively connected to the first electrical contacts of the first housing part. These measures ensure that the high-pressure discharge lamp and the primary of the ignition transformer automatically make electrical contact, during assembly of the base, with the control unit components accommodated in the second housing part.